I have a 1985 300d turbo diesel with 219,000 miles. It is running great, with good acceleration and (I think) a normal amount of engine noise. I think it has always been well cared for. The timing chain is original. I am the third owner.

My local mechanic tells me I should replace the timing chain. He says he has seen these timing chains break in the 250,000-mile range, requiring an engine rebuild. My old mechanic across town feels this is unnecessary.

Please let me know what you think.
Thanks!
-Joe

Job # 05-215 tells how to check for stretch, both by "eyeballing" it and with the dial gauge. At 220K, I'd guess it's about due, but have 'em check it. No reason to guess.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

That's the thing to do. Check it before spending the money for nothing. I have the same car and I think I checked mine with about that same mileage. It had nearly no stretch at all. This is a car that routinely had 3K mile oil changes since new.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

The only reason to change the timing chain is due to stretch that is over factory tolerances (I think 5 degrees is the accepted go/no-go point). I would like to point out that the general agreement here is that the chain usually doesn't break: the tensioner fails or the plastic chain guides crack and fail. Then the chain fails due to one of those reasons.

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84 300DT Puke Yellow. Totalled after 438,000
84 300DT Orient Red. 169,000 (actual mileage may vary)
2002 Explorer EB (wife's)

Thanks for your advice. It sounds like this is a question of risk tolerance. If one is risk-averse, then prophylactically changing the chain is good insurance, or peace of mind. I can live with some small risk, and so will probably leave the chain alone.

By the way, my friend's 124 turbo diesel (1990, I think) had the timing chain go out while still under warranty. The car was maybe 2 years old. Guess they don't make 'em like they used to...

It sounds to me like the chain is in no danger of failing unless it is stretching, indicating link wear.

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'83 240D with 617.952 and 2.88
'01 VW Beetle TDI
'05 Jeep Liberty CRD
'89 Toyota 4x4, needs 2L-T
'78 280Z with L28ET - 12.86@110
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Katanaz,

Bear in mind that timing chains don't "stretch", they elongate from the wear on the pins and bushings, thus making the chain actually longer because the chain pitch increases slightly.

I agree with the mechanic that says replacement is not necessary as long as the cam timing is not more than 5* late.

P E H

Hey,
I was wondering about this. The tensioner comes out pretty easy but how easy is it to replace the plastic guides?

Sorry for hijacking the thread but it seamed like your question was answered.

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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The guides are all held in place with roll pins. The top one is easy to get out, the big banana slide on the rt side is a little tougher, the slide underneath is just this side of impossible without having the engine out.
There is a very good write up in the Haynes manual, basically you will need to remove the tensioner and the lower roll pin to pull that big slide out. You can see the head of it on the front of the engine assembly, down below the top of the slide itself. There are a few parts to get off first, the fan clutch and the half round cover over the front crank seal need to be removed.
The top plastic guide is held there with a smaller roll pin also, take a look at it next time you have the valve cover off, that one is easy to get off. Should replace those roll pins when replacing the guides also. Install them with a little sealant to hold them in place.

OK, after reading the thread, I'm still not clear on this point: has the elongation of the chain been measured?

My chain just broke in my 1980 240D at 210k miles. I have no idea if it was stretched and I haven't pulled all of the rails yet to check for damage.

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Rich Mason
Chapel Hill, NC
1990 300D 285k miles
1993 VW Cabriolet converted to 1.6 TD
1985 VW Westfalia 1.6 TD

Mechanics like to tell their customers to replace the chain because it's something that doesn't take very long but they can charge a lot for. I did a visual inspection of the timing chain area on my cars, including checking for stretch and I'm not gonna touch it as it's only 2-3 degrees stretched. Some of the most experienced members on this board have said that chains don't break on their own. They occasionally break because either they get jammed by something else or an improperly installed master link on a new chain disconnects. I firmly believe the timing chain is one of those items that is covered under the "if it ain't broke don't fix it" policy.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

The engine on these diesels is known to back up at shut off on occasion., to lurch backwards. One theory is that if the chain is well worn and if the guides are worn, it can bunch up in there and start a tear in on of the links. From there only matter of time before it lets go.

I'd rather fix the timing chain on an interferance motor BEFORE it breaks....thanyouverymuch. It would cost far more to wait till after.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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